Reusable nip measuring device and method

ABSTRACT

A device and method for measuring heat and pressure of a fusing nip formed between heat and pressure fusing rolls for fusing powder images onto copy sheets. The nip measuring device consists of two polyimide sheets each having a thickness ranging from 3 to 8 mils and one of which is coated with silicone rubber material. The two sheets are positioned between the opened nip of heat and pressure fusing rolls which are then closed for a predetermined time. Upon separation of the rolls the two sheets are removed and observed. A distinct pattern is formed on the uncovered sheet from the rubber coating on the second sheet indicating immediately contact arc and pressure characteristics of the fusing nip. Upon separation of the sheets the pattern is removed due to a neutralization of electrostatic surface forces holding the sheets together.

United States Patent Thettu Sept. 23, 1975 1 REUSABLE NIP MEASURING DEVICE AND METHOD [75] inventor: Reghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Aug. 19, 1974 [2]] Appl. No.1 498,491

[52] US. Cl 73/432 R [51] Int. Cl. G01L 5/00 [58] Field of Search 73/432 R, 172

[56] References Cited UNITED STATES PATENTS 2,860.416 11/1958 Pfund 73/172 Primary ExaminerS. Clement Swisher Assistant Examiner-Denis E. Corr 1 1 ABSTRACT A device and method for measuring heat and pressure of a fusing nip formed between heat and pressure fusing rolls for fusing powder images onto copy sheets. The nip measuring device consists of two polyimide sheets each having a thickness ranging from 3 to 8 mils and one of which is coated with silicone rubber material. The two sheets are positioned between the opened nip of heat and pressure fusing rolls which are then closed for a predetermined time. Upon separa-.

tion of the rolls the two sheets are removed and observed. A distinct pattern is formed on the uncovered sheet from the rubber coating on the second sheet in dicating immediately contact are and pressure characteristics of the fusing nip. Upon separation of the sheets the pattern is removed due to a neutralization of electrostatic surface forces holding the sheets to gether.

3 Claims, 5 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 2 3,906,800

iiiiillii REUSABLE NIP MEASURING DEVICE AND METHOD I This invention relates to an improved device and powder into direct contact with a hot surface, such as a heated roller. The roller surface may be dry, i.e., no application of a liquid release agent to the -surface of that roller as described, for example, in U.S. Pat. Nos. 3,498,596, 3,539,161 and 3,666,247. Alternatively, the fuser roll surface may be melted'witha releaseagent such as silicone oil as described in U.S. Pat; Nos. 3,268,351 and 3,256,002. 7

It has been found that the measurement of the contact are and the pressure in the nip of the rolls is desirable from the standpoint of adjusting the nip to obtain high quality fixing of copy sheets. Therefore, the ease with which these parameters can beimmediately ascertained under varying conditions can beextremely advantageous in the set up of a machine in the-minimum time. i

The present invention is for a method and device for rapidly ascertaining the pressure and contact are of thenip formed by pressure fusing rolls used in reproduction machines. This is accomplished, generallyspeaking, by offsetting a portion of a toner pattern from a strip onto another strip for immediate analysis. The present invention is particularly intended to be an im-' provement over copending application Ser. No. 370,182 commonly assigned herewith.

It is therefore the principle object of the present invention to improve pressure fusing roll devices.

It is a further object of the present invention to facilitate the measurement of pressure and contact are characteristics in the nip of fusing rolls.

It is a further object of the present invention. to improve significantly the quality of fixes produced by pressure fusing rolls. I

It is a further object of the present invention to detect wear and/or damage in the construction of pressure fusing rolls. I

These as well as other objects of the invention and further features thereof will be better understood upon reference to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. 1 illustrates schematically a xerographic reproducing apparatus incorporating a heated pressure fuser roll apparatus to be measured in accordance with the present invention;

FIGS. 2a and 2b are side views of the fusing rolls illustrating the measurement steps in sequence;

FIG. 3 is an enlarged portion of the device of the invention after measuring pressure and contact are characteristics of; and I FIG. 4 is a view similar to FIG. 3 illustrating the separation of the sheets of the device to remove a characteristic pattern thereon.

Referring now to the drawings, there is shown in FIG. 1 an automatic xerographic reproducing machine incorporating heat and pressure fusing rolls to be measured according to the invention. The automatic xerographic reproducing machine includes a xerographic plateor surface 10 formed in the shape of a drum. The

plate has a photoeonduetivelayer or light receiving sur-' face on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow.The rotation will cause the plate surface to sequentially pass a series'of xer'ographic processing stations. For the purpose of the present disclosure the several xerographic processing stations in'the' path of movement of the plate surface may be described functionally as follows: A charging station A at which a uniform electrostatic charge is deposited on the photoeonductive plate;

An exposure station'B,'at which light or a radiation pattern of copies to be reproduced is projected onto static image to form a toner powder image in configuration'of the copy being reproduced;

'A transfer station D at which the toner powder image is electrostatically transferred from the plate surface to source to effect substantially complete discharge of any residual electrostatic charge remaining thereon, and

A fusing station F at which the toner powder image is affixed to the paper support material by fusing rolls 103 and which apply heat and pressure.

The processing description of' the xerographic process is sufficient for an understanding of the instant in vention. Further details maybe had by reference to U.S.' Pat. No. 3,s78;ss9 filed July 3, 1969, and commonly assigned herewith. I

In accordance with the inven'tion the quality of the copies provided by the machine isaffected by the fusing characteristics at the nip formed fuser roll 103 and' pressure roll 105 through the copy sheet to be fused is advanced. V v

The fusingrolls may be wetted or dry described above. In either case the nip pressure and heat are critical in obtaining high quality fusing. For the dry system the fuser roll comprises a rotating member having an elastic compressible coating 132 made of silicone rubber or any suitable heat resistant compressible material as described, for example, in the aforementioned patents. The rotating member may internally heated by a heat source 134 as described in U.S. Pat. No. 3,666,247 or externally heated as described in U.S. Pat. No. 3,498,596 and 3,539,161. The pressure roll comprises a rotating member which is covered with an elastic layer 142 of a slightly higher durometer than the fuser roll coating 132 as described in the aforementioned patents. The subject invention is concerned with the immediate determination of the heat and pressure characteristics of the nip.

Referring specifically to FIGS. 2a and 2h there is shown the steps for measuring the contact are or nip formed by the fusing rollers. The measurement device 200 comprises two sheets 201 and 210 which are made of a polyimide material and which have a thickness ranging from about .003 to about .008 inches. A preferred sheet material is manufactured under the tradename Kapton by DuPont Corporation, Wilmington, Delaware. Sheet 210 has a coating 215 which is made of silicone rubber which has a thickness of about .002 to about .004 inches. Suitable coating materials are manufactured by General Electric Co. under the tradenames 100, 108, 112 and 102 by Dow Corning under the tradenames 236 and 735 and combinations thereof.

Sheets 201 and 210 are inserted between the fusing rollers 103 and 105 while the rollers are separated. Next the fusing rollers are closed to form an operating nip for a predetermined time. Preferably this time ranges from about 5 to about 7 seconds. in the final step the fusing rollers are removed from each other to an inoperative position and the sheets 201 and 210 removed.

It has been observed that sheet 201 will have a distinct impression formed from the silicone rubber coating 215. As understood the elastomeric coating when under compression stretches and provides intimate contact with the surface in contact therewith. The surface is held into contact with the elastomeric coating after release of the pressure of the nip due to electrostatic surface forces. Sheet 201 is transparent enabling instant detection of the nip characteristics, such as, contact are width with the human eye. Upon separation of the sheets the impression is removed for reuse of the device.

The operation of the measuring device is best understood from FlGS. 3 and 4. In FIG. 3 the width of the impression pattern 220 is used to determine the contact are width of the fusing rollers. Thus if there is too much pressure there will be an increase over the standard nip width normally observed for the machine operation conditions. On the other hand, if there is insufficient pressure in the nip the width will be decreased from the standard.

Furthermore, it will be observed that since the materials ofthe device are heat stable there is no effect from the high temperatures associated with pressure heated fusing rollers. Upon separation of the sheets the im pression disappears as best shown in FIG. 4. In this LII manner the device can be used over and over again Lil until the desired operating conditions are obtained. The pattern will not fade and is reusable if desired.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

l. A device for measuring heat and pressure of a fusing nip between heat and pressure fusing rolls comprising:

a first sheet of polyimide film material having a thickness ranging from about .003 to about .008 inches. said first sheet being transparent,

a second sheet of polyimide film material positioned in overlying relationship with said first sheet, sait second sheet having a coating of silicone rubbe. material of a thickness ranging from about .002 tr about .004 inches, and

nip means for applying pressure to said sheets for a predetermined time whereby upon separation 01 the sheets from said nip means is formed on said first sheet indicating pressure and contact are characteristics of the nip means.

2. A method of measuring heat and pressure of a fusing nip between heat and pressure fusing rolls comprising the steps;

positioning the first and second sheets of heat stable polyimide material with one of said sheets having a thin elastomeric coating thereon in overlying relationship, at least a one of said sheets being transparent, I

inserting said first and second sheets between pressure fusing rolls while spaced apart,

closing the rolls to form a nip at operating conditions for a predetermined time, and

separating the rolls and removing said sheets from the fusing rolls to observe pressure characteristics of the nip.

3. A method according to claim 2 wherein said elastomeric material is silicone rubber having a thickness ranging from about .002 to about .004 inches. 

1. A DEVICE FOR MEASURING HEAT AND PRESSURE OF A FUSING NIP BETWEEN HEAT AND PRESSURE FUSING ROLLS COMPRISING: A FIRST SHEET OF POLYIMIDE FILM MATERIAL HAVING A THICKNESS RANGING FROM ABOUT .003 TO ABOUT .008 INCHES SAID FIRST SHEET BEING TRANSPARENT, A SECOND SHEET OF POLYIMIDE FILM MATERIAL POSITIONED IN OVERLYING RELATIONSHIP WITH SAID FIRST SHEET, SAID SECOND SHEET HAVING A COATING OF SILICONE RUBBER MATERIAL OF A THICKNESS RANGING FROM ABOUT .002 TO ABOUT .004 INCHES, AND NIP MEANS FOR APPLYING PRESSURE TO SAID SHEETS FOR A PREDETERMINED TIME WHEREBY UPON SEPARATION OF THE SHEETS
 2. A method of measuring heat and pressure of a fusing nip between heat and pressure fusing rolls comprising the steps; positioning the first and second sheets of heat stable polyimide material with one of said sheets having a thin elastomeric coating therEon in overlying relationship, at least a one of said sheets being transparent, inserting said first and second sheets between pressure fusing rolls while spaced apart, closing the rolls to form a nip at operating conditions for a predetermined time, and separating the rolls and removing said sheets from the fusing rolls to observe pressure characteristics of the nip.
 3. A method according to claim 2 wherein said elastomeric material is silicone rubber having a thickness ranging from about .002 to about .004 inches. 